Pyridazodiazepine derivatives

ABSTRACT

Compounds of the formula    &lt;IMAGE&gt;  I  wherein R1 and R2 each independently represent hydrogen, C1-C10-alkyl, adamantyl-(C1-C4-alkyl) or (C2-C6-alkanoyloxy)-(C1-C4-alkyl), and pharmaceutically acceptable salts thereof possess antihypertensive activity and can be used as theraputic or prophylactic agents in pharmaceutical preparations. Intermediates for the production of such compounds are also provided.

DESCRIPTION OF THE INVENTION

The present invention is concerned with pyridazodiazepine derivatives,pharmaceutical preparations containing such derivatives as a therapeuticagent, and a method of treating or preventing hypertension using suchderivative compounds.

The pyridazodiazepine derivatives of the present invention are compoundsof the formula ##STR2## wherein R¹ and R² each independently arehydrogen, C₁ -C₁₀ -alkyl, adamantyl-(C₁ -C₄ -alkyl) or (C₂ -C₆-alkanoyloxy)-(C₁ -C₄ -alkyl), as well as pharmaceutically acceptablesalts thereof.

The compounds of formula I contain three asymmetric carbon atoms and cantherefore exist as optically pure diastereoisomers, as diastereoisomericracemates or as mixtures of different diastereoisomeric racemates. Thepresent invention includes within its scope all of these possible forms.In the compounds of formula I the configuration at each of theasymmetric carbon atoms is preferably (S).

As used throughout this disclosure, the terms "C₁ -C₄ -alkyl" and "C₁-C₁₀ -alkyl" mean straight-chain or branched-chain alkyl groups whichcontain the respective number of carbon atoms. Examples of such alkylgroups include methyl, ethyl, propyl, isopropyl, butyl, tert.butyl,n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, and the like.The term "C₂ -C₆ -alkanoyloxy" means an alkanoyloxy group derived from astraight-chain or branched-chain alkanecarboxylic acid containing up to6 carbon atoms (for example, acetic acid, propionic acid, butyric acid,pivalic acid, and so forth).

The compounds of formula I form pharmaceutically acceptable salts withacids. Examples of such salts are mineral acid salts such ashydrohalides (for example, hydrobromides, hydrochlorides, and so forth),sulphates, phosphates, nitrates, and so forth, and organic acid saltssuch as acetates, maleates, fumarates, tartrates, citrates, salicylates,methanesulphonates, p-toluenesulphonates, and so forth. The compounds offormula I in which R¹ and/or R² are hydrogen also form pharmaceuticallyacceptable salts with bases. Examples of such salts are alkali metalsalts (for example, sodium and potassium salts), alkaline earth metalsalts (for example, calcium and magnesium salts), ammonium salts andsalts with organic amines (for example, dicyclohexylamine salts).

In formula I above, R¹ preferably is hydrogen, C₁ -C₁₀ -alkyl oradamantyl-C₁ -C₄ -alkyl), especially hydrogen, ethyl, n-decyl orl-adamantylethyl. R² preferably is hydrogen or (C₂ -C₆ -alkanoyloxy)-(C₁-C₄ -alkyl), especially hydrogen or pivaloyloxymethyl. With respect tothe guanidino group H₂ N--C(NH)--NH in the compounds of formula I, thisis preferably situated in the para-position of the phenyl ring.

As will be evident from the foregoing, especially preferredpyridazodiazepine derivatives provided by the present invention arethose in which R¹ is hydrogen, ethyl, n-decyl or l-adamantylethyl, R² ishydrogen or pivaloyloxymethyl, and the guanidino group is present in thepara-position of the phenyl ring.

The most preferred pyridazodiazepine derivatives provided by the presentinvention are9(S)-[1(S)-carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid and its pharmaceutically acceptable salts, particularly thedihydrobromide.

Examples of other interesting pyridazodiazepine derivatives of thepresent invention are:

9(S)-[1(S)-Ethoxycarbonyl-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid,

9(S)-[1(S)-(n-decyloxycarbonyl)-3-(4-guanidinophenyl)-propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid,

9(S)-[1(S)-[[2-(1-adamantyl)ethoxy]carbonyl]-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylic acid, and

9(S)-[1(S)-ethoxycarbonyl-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pivaloylxymethyl ester, as well as their pharmaceuticallyacceptable salts.

Compounds of formula I and their pharmaceutically acceptable salts arecan be prepared by

(a) catalytically hydrogenating a compound of the formula ##STR3##wherein R¹ and R² have the same meaning given above, and R³ is hydrogenor benzyl, in an acidic medium and converting any resultingnon-pharmaceutically acceptable acid addition salt of a compound offormula I into a compound of formula I, or

(b) for the preparation of a compound of formula I in which R¹ and/or R²are hydrogen, treating a compound of formula I in which R¹ and/or R² areC₁ -C₁₀ -alkyl with an acid and/or a base, or

(c) if desired, separating a mixture of diastereoisomeric racemates intothe diastereoisomeric racemates of optically pure diastereoisomers, or

(d) if desired, resolving a racemate obtained into the opticalantipodes, or

(e) if desired, converting a compound of formula I obtained into apharmaceutically acceptable salt or converting a pharmaceuticallyacceptable acid addition salt of a compound of formula I obtained into acompound of formula I.

The catalytic hydrogenation of a compound of formula II in an acidicmedium in accordance with embodiment (a) of the process yields an acidaddition salt of a compound of formula I. The catalytic hydrogenationcan be carried out, for example, in the presence of a platinum orpalladium catalyst which may be supported on an inert carrier material.Palladium-on-carbon is an especially suitable catalyst. The catalytichydrogenation is preferably carried out in an acidic medium which yieldsa pharmaceutically acceptable acid addition salt of a compound offormula I, conveniently a suitable alkanecarboxylic acid such as aceticacid, aqueous hydrochloric acid, aqueous hydrobromic acid or a mixtureof one of these aqueous acids with a lower alkanecarboxylic acid. In afurther embodiment, the acidic medium may be provided, at leastpartially, by using an acid addition salt of the compound of formula II.Conveniently, the catalytic hydrogenation is carried out at about roomtemperature and under atmospheric pressure.

When the catalytic hydrogenation yields a non-pharmaceuticallyacceptable acid addition salt of a compound of formula I, this salt isconverted into a compound of formula I. This conversion can be carriedout by treatment with a base under conditions that will be apparent tothose skilled in the art.

According to embodiment (b) of the process, a compound of formula I inwhich R¹ and/or R² are C₁ -C₁₀ -alkyl is converted into a compound offormula I in which R¹ and/or R² are hydrogen by treatment with an acidand/or a base, as the case may require depending on the nature of the C₁-C₁₀ -alkyl group. This embodiment can be carried out, for example, whenR¹ and/or R² are tert.-butyl, by treatment with an appropriate acid suchas hydrogen bromide in acetic acid or trifluoroacetic acid,advantageously at about room temperature. Again, for example, when R¹and/or R² are C₁ -C₁₀ -alkyl other than tert.butyl, the treatment can becarried out using an appropriate base such as an aqueous ethanolicalkali metal hydroxide (for example, aqueous ethanolic sodium hydroxideor aqueous ethanolic potassium hydroxide) or aqueous ammonia at atemperature between about room temperature and the boiling point of thereaction mixture, advantageously at about room temperature.

The separation of a mixture of diastereoisomeric racemates into thediastereoisomeric racemates or optically pure diastereoisomers inaccordance with embodiment (c) of the process can be carried out, forexample, by chromatography (such as on silica gel) using a suitablesolvent system (such as ethyl acetate/n-hexane, toluene/ethyl acetate,and the like).

The resolution of a racemate into the optical antipodes in accordancewith embodiment (d) of the process can be carried out, for example, bytreatment with an appropriate optically active acid or base as the casemay require, separating the optically active salts obtained (forinstance, by fractional crystallization) and, where required, liberatingthe optically uniform compounds from these salts by conventionaltechniques.

The conversion of a compound of formula I into a pharmaceuticallyacceptable salt in accordance with embodiment (e) of the process can becarried out in a manner known per se by treatment with an appropriateacid or, where R¹ and/or R² in the compound of formula I are hydrogen,by treatment with an appropriate base. The conversion of apharmaceutically acceptable acid addition salt of a compound of formulaI into a compound of formula I, also in accordance with embodiment (e)of the process, can be carried out by treatment with an appropriatebase.

The compounds of formula II which are used as starting materials can beprepared, for example, by reacting a compound of the formula ##STR4##wherein R³ represents hydrogen or benzyl and R²⁰ represents C₁ -C₁₀-alkyl, with a compound of the formula ##STR5## wherein R¹⁰ is C₁ -C₁₀-alkyl and Q is a leaving atom or group, to give a compound of theformula ##STR6## wherein R³, R¹⁰ and R²⁰ have the same meanings as givenabove, and, if desired, treating a compound of formula V with an acidand/or a base to give a compound of the formula ##STR7## wherein R³ hasthe meaning given above and R¹¹ and/or R²¹ are hydrogen, and, also ifdesired, esterifying a compound of formula VI to give a compound of theformula ##STR8## wherein R³ has the meaning given above and R¹² and/orR²² are C₁ -C₁₀ -alkyl (other than the C₁ -C₁₀ -alkyl denoted by R¹⁰ andR²⁰ in formula V), adamantyl-(C₁ -C₄ -alkyl) or (C₂ -C₆-alkanoyloxy)-(C₁ -C₄ -alkyl).

The leaving atom or group denoted by Q in a compound of formula IV canbe any conventional leaving atom or group; for example, a halogen atomsuch as a bromine atom or a sulphonate group of the formula --O--SO₂ Yin which Y is a methyl, trifluoromethyl, p-tolyl, 4-nitrophenyl, or thelike.

The reaction of a compound of formula III with a compound of formula IVto give a compound of formula V can be carried out in a known manner,conveniently in the presence of an inert organic solvent such asacetonitrile, dimethyl sulphoxide, dimethylformamide, or the like, andin the presence of an acid-binding agent such as an alkali metalcarbonate (for example, sodium carbonate), a basic ion-exchange resinor, preferably, a tertiary organic base (for example, triethylamine).The reaction can be carried out at a temperature from about 0° C. up tothe boiling point of the reaction mixture.

The treatment of a compound of formula V with an acid and/or a base togive a compound of formula VI can be carried out in a manner known perse. The particular treatment which is required will, of course, dependon the nature of the C₁ -C₁₀ -alkyl groups present in the compound offormula V. For example, when R¹⁰ and/or R²⁰ are tert.butyl, thetreatment can be carried out using an appropriate acid such as anhydroustrifluoroacetic acid, conveniently at about room temperature, orhydrogen bromide in acetic acid, also conveniently at about roomtemperature. Again, for example, when R¹⁰ and/or R²⁰ are C₁ -C₁₀ -alkylother than tert.butyl the treatment can be carried out using anappropriate base such as an aqueous ethanolic alkali metal hydroxide(for instance, aqueous ethanolic sodium hydroxide or aqueous ethanolicpotassium hydroxide) or aqueous ammonia at a temperature between aboutroom temperature and the boiling point of the reaction mixture, mostadvantageously at about room temperature.

The esterification of a compound of formula VI to give a compound offormula VII can be carried out, for example, by treatment of thecompound of formula VI with a suitable alkanol or appropriatelysubstituted alkanol in the presence of N,N'-dicyclohexylcarbodiimide.Again, for example, a compound of formula VI in which R³ is benzyl canbe esterified by treatment with a suitable alkyl bromide orappropriately-substituted alkyl bromide in the presence of a strong base(for instance, potassium hydroxide) or cesium carbonate.

Subsequently, a compound of formula V, VI or VII is reduced to give acompound of the formula ##STR9## wherein R¹, R² and R³ have the meaningsgiven above.

The reduction of a compound of formula V, VI or VII to give a compoundof formula VIII can be carried out, for example, by catalytichydrogenation in the presence of a noble metal catalyst such as platinumor palladium which may be supported on an inert carrier material.Palladium-on-carbon can be mentioned as an especially suitable catalystfor the present purpose. This catalytic hydrogenation is advantageouslycarried out in an inert organic solvent, particularly an alkanol such asmethanol, ethanol and so forth, at room temperature and underatmospheric pressure. Again, for example, the reduction can be carriedout using zinc/acetic acid according to known techniques.

A compound of formula VIII in which R¹ and/or R² are C₁ -C₁₀ -alkyl can,if desired, be converted into a compound of formula VIII in which R¹and/or R² are hydrogen by treatment with an acid and/or a base. Thistreatment can be carried out in the same manner as described earlier inconnection with the conversion of a compound of formula V into acompound of formula VI.

A compound of formula VIII is subsequently reacted with1-nitroguanyl-3,5-dimethylpyrazole to give a compound of formula II.

The reaction of a compound of formula VIII with1-nitroguanyl-3,5-dimethylpyrazole can be carried out in the presence ofan inert organic solvent, particularly an alkanol such as methanol,ethanol, or the like, and at an elevated temperature, preferably at thereflux temperature of the reaction mixture.

A compound of formula II in which R¹ and/or R² are C₁ -C₁₀ -alkyl can,if desired, be converted into a compound of formula II in which R¹and/or R² are hydrogen by treatment with an acid and/or a base. Thistreatment can be carried out in the same manner as described earlier inconnection with the conversion of a compound of formula V into acompound of formula VI.

The compounds of formulae II, V, VI, VII and VIII which can berepresented collectively by the formula ##STR10## wherein R¹, R² and R³have the meanings given earlier and S is nitro, amino or2-nitroguanidino, form part of the present invention.

The compounds of formula III in which R³ is hydrogen are known compoundsor analogs of known compounds. The compounds of formula III in which R³is benzyl can be prepared by reductively benzylating a compound offormula III in which R³ is hydrogen.

The compounds of formula IV are known compounds or analogs of knowncompounds.

The pyridazodiazepine derivatives provided by the present inventioninhibit angiotensin converting enzyme (ACE) which brings about theconversion of angiotensin I into angiotensin II and are therefore usefulas antihypertensive agents. Moreover, they have an unexpectedlyprolonged duration of activity.

The activity of the present pyridazodiazepine derivatives in inhibitingangiotensin-converting enzyme in vitro can be determined using the testnow described.

The method used is based on the method of Santos, R. A. S., Kreiger, E.M., and Greene L. J., Hypertension (1985), 7, 244-252. Angiotensinconverting enzyme (rabbit lung) is incubated in the presence or absenceof various concentrations of a test substance for 90 minutes at 37° C.in 0.1M potassium phosphate buffer, pH 7.5, containing 30 mmol of sodiumchloride. If the test substance is an ester, it is cleaved by treatmentwith hog liver esterase prior to carrying out the test. The reaction isinitiated by adding angiotensin I to a final concentration of 250 μmol.The final volume of the reaction mixture is 0.25 ml. After holding thereaction mixture at 37° C. for 30 minutes the reaction is terminated byadding 1.45 ml of 0.3M sodium hydroxide solution. 100 ml of a 0.2%(weight/volume) solution of o-phthaldialdehyde in methanol are addedand, after 10 minutes, the solution is acidified with 200 μl of 3Mhydrochloric acid. The resulting solution is then subjected tofluorescence spectrometry using excitation and emission wavelengths of365 nm and 500 nm, respectively, and the IC₅₀ value is calculated. TheIC₅₀ is that concentration of test substance which reduces by 50% theconversion of angiotensin I into angiotensin II.

In the test described above,9(S)-[1(S)-carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid dihydrobromide exhibits an IC₅₀ of 0.6 nmol.

The pyridazodiazepine derivatives of the present invention can be usedas therapeutic substances in the form of pharmaceutical preparationswhich contain them in association with a compatible pharmaceuticalcarrier material. This carrier material can be an organic or inorganiccarrier material which is suitable for enteral (for example, oral) orparenteral administration. Examples of such carrier materials are water,gelatin, gum arabic, lactose, starch, magnesium stearate, talc,vegetable oils, polyalkylene glycols and petroleum jelly. Thepharmaceutical preparations can be made up in solid form (for example,as tablets, dragees, suppositories or capsules) or in a liquid form (forexample, as solutions, suspensions or emulsions). The pharmaceuticalpreparations may be subjected to standard pharmaceutical operations suchas sterilization and/or may contain adjuvants such as preserving,stabilizing, wetting or emulsifying agents, salts for varying theosmotic pressure, or buffers. The pharmaceutical preparations may alsocontain other therapeutically useful substances.

The pyridazodiazepine derivatives provided by the present invention canbe administered to adults in a daily dosage from about 0.1 mg to 100 mg,preferably about 1 mg to 50 mg, per kilogram of body weight. The dailydosage may be administered as a single dose or in divided doses. It willbe appreciated that the aforementioned dosage range is given by way ofillustration only and can be varied upwards or downwards depending onfactors such as the particular derivative being administered, the routeof administration, the severity of the indication being treated and thecondition of the patient as determined by the attending physician.

The compounds of formula IX in which R³ is hydrogen also inhibitangiotensin-converting enzyme and can be used as antihypertensives.

The following Examples further illustrate the present invention:

EXAMPLE 1

A solution of 0.70 g of9(S)-[1(S)-carboxy-3[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid hydrobromide in a mixture of 16 ml of acetic acid, 4 ml of waterand 4 drops of hydrobromic acid was hydrogenated over 10%palladium-on-carbon at room temperature and under atmospheric pressurefor 72 hours. The catalyst was removed by filtration and the filtratewas evaporated. The residual oil was dissolved in 50 ml of water and thesolution was lyophilized to give 0.735 g of9(S)-[1(S)-carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid dihydrobromide as an off-white amorphous solid.

NMR: δ_(H) (CD₃ OD, 300 MHz): 1.44 (1H, m), 1.68-1.98 (4H, m), 2.04-2.36(4H, m), 2.42 (1H, m), 2.63 (1H, m), 2.82-2.98 (2H, m), 3.04 (1H, broad,d), 3.17 (1H, m), 3.48 (1H, m), 4.01 (1H, t), about 4.90 (2H, obscured),7.25 (2H, d) and 7.41 (2H, d).

MS: m/e 447 (20% [M+H]⁺) and 211 (100).

The9(S)-[1(S)-carboxy-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid hydrobromide used as the starting material was prepared as follows:

(A)(i) A solution of 0.566 g of tert.butyl9(S)-amino-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylate,0.688 g of tert.butyl 2(R,S)-bromo-4-(4-nitrophenyl)butanoate and 0.202g of triethylamine in 12 ml of acetonitrile was heated to 80° C. for 16hours. The solvent was removed by evaporation and the residue waspartitioned between water and dichloromethane. The organic solution wasevaporated and the resulting oil was chromatographed on silica gel.Elution with toluene/ethyl acetate (1:1) gave 0.195 g of tert.butyl9(S)-[1(R)-tert.butoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas a yellow oil and, subsequently, 0.252 g of tert.butyl9(S)-[1(S)-tert.butoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas a yellow oil.

Analysis for C₂₈ H₄₂ N₄ O₇ : Calculated: C: 61.5; H: 7.70; N: 10.25%.Found: C: 61.5; H: 7.75; N: 10.20%.

A(ii)(a) A solution of 18 g of 2(R)-hydroxy-4-phenylbutanoic acid in 200ml of dichloromethane containing 20.5 g of triethylamine and 250 mg of4-(dimethylamino)pyridine was stirred at room temperature and treateddropwise with 12 g of acetic anhydride. The resulting mixture wasstirred for a further 3 hours and then acidified by the addition of 125ml of 2N sulphuric acid. The organic phase was separated and washed withtwo 100 ml portions of 2N sulphuric acid, then with 100 ml of water andfinally with 100 ml of saturated sodium chloride solution, dried overanhydrous magnesium sulphate and evaporated in vacuo to give 22 g of2(R)-acetoxy-4-phenylbutanoic acid as a colouless viscous oil; [α]₄₃₆ ²⁰=+13.7° (c=1 in ethanol).

(b) A solution of 22 g of 2(R)-acetoxy-4-phenylbutanoic acid in 10 ml ofglacial acetic acid was added dropwise to a cooled (-5° C.) and stirrednitrating mixture, prepared by the dropwise addition of 12.6 g of fuming95% nitric acid to 41 g of acetic acid while maintaining the internaltemperature at about 5° C. throughout by means of an external coolingbath (-10° C. to -5° C.) and finally allowing the temperature of thenitrating mixture to fall to -5° C. The resulting mixture was stirred at-5° C. for a further 2 hours, poured into about 200 ml of ice-water andstirred for several hours. The mixture was extracted with three 100 mlportions of diethyl ether, the combined organic extracts were washedwith three 100 ml portions of water and with 100 ml of saturated sodiumchloride solution, dried over anhydrous magnesium sulphate andevaporated in vacuo to give 27 g of a pale yellow oil consisting of amixture of 2(R)-acetoxy-4-(2-nitrophenyl)butanoic acid and2(R)-acetoxy-4-(4-nitrophenyl)butanoic acid in the approximate ratio 1:2as determined by ¹ H-NMR spectroscopy. This oil was dissolved in 50 mlof warm toluene and left to crystallize for several hours at 0°-5° C. togive 9.6 g of 2(R)-acetoxy-4-(4-nitrophenyl)butanoic acid as a colorlesscrystalline solid having a melting point of 108°-109° C.

(c) 8.0 g of 2(R)-acetoxy-4-(4-nitrophenyl)butanoic acid were addedportionwise to a stirred solution of 4 g of tert.butanol, 7 g ofN,N'-dicyclohexylcarbodiimide and 450 mg of 4-pyrrolidinopyridine in 200ml of dichloromethane and the mixture was stirred at 0° C. for 16 hours.The mixture was filtered and the filtrate was washed in succession with100 ml of water, two 100 ml portions of 2N acetic acid, 100 ml of water,two 100 ml portions of saturated sodium bicarbonate solution and 100 mlof saturated sodium chloride solution, dried over anhydrous magnesiumsulphate and evaporated in vacuo to give 10 g of a pale yellowsemi-solid residue. This residue was triturated with a small amount ofdiethyl ether and filtered, and the filtrate was eluted through a silicagel column with diethyl ether/n-hexane (1:1) to give 9 g of tert.butyl2(R)-acetoxy-4-(4-nitrophenyl)butanoate as a pale yellow oil; MS m/e 324(10%, [M+H]⁺) and 268 (100%).

(d) 8.0 g of tert.butyl 2(R)-acetoxy-4-(4-nitrophenyl)butanoate weredissolved in 200 ml of methanol saturated with ammonia at 0° C. and themixture was stirred for 16 hours. Evaporation of the mixture in vacuogave 7 g of an almost colorless oil which was dissolved in an equalvolume of diethyl ether/n-hexane (1:1) and eluted through a silica gelcolumn with the same solvent mixture to give 6 g of tert.butyl2(R)-hydroxy-4-(4-nitrophenyl)butanoate as a colorless crystalline solidhaving a melting point of 41°-42° C.

(e) A solution of 0.4 ml of dry pyridine in 20 ml of dichloromethane(dried over molecular sieve) was cooled to -20° C. while stirring underanhydrous conditions and then treated dropwise with 1.4 g oftrifluoromethanesulphonic anhydride. After 5 minutes a solution of 1.4 gof tert.butyl 2(R)-hydroxy-4-(4-nitrophenyl)butanoate in 5 ml of drydichloromethane was added and the resulting mixture was stirred at 0° C.for 16 hours. The mixture was filtered through a silica gel column andthe column was washed with two 10 ml portions of dry dichloromethane.The combined filtrates, containing tert.butyl2(R)-trifluoromethanesulphonyloxy-4-(4-nitrophenyl)butanoate, weretreated with 0.5 g of dry triethylamine and 1.4 g of tert.butyl9(S)-amino-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateand the mixture was stirred at room temperature for 1 hour. The mixturewas washed in succession with 25 ml of water, 25 ml of saturated sodiumbicarbonate solution and 25 ml of saturated sodium chloride solution,dried over anhydrous magnesium sulphate and evaporated in vacuo to give3 g of a yellow oil. Chromatography on silica gel using diethyl etherfor the elution gave 1.7 g (60%) of tert.butyl9(S)-[1(S)-tert.butoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas a yellow oil which was identical with the compound obtained accordingto the procedure described in paragraph (A)(i).

(A)(iii)(a) A solution of 2.8 g of tert.butyl2(R)-hydroxy-4-(4-nitrophenyl)butanoate, prepared as described inparagraph (A)(ii)(d), and 2 ml of dry triethylamine in 20 ml of drydichloromethane were added dropwise to a stirred solution, cooled to 0°C., of 2.2 g of 4-nitrobenzenesulphonyl chloride in 40 ml of drydichloromethane and the mixture was stirred at 0° C. for 16 hours. Theresulting solution was washed in succession with 50-ml of water, three50 ml portions of 1N sulphuric acid, 50-ml of water, two 50 ml portionsof saturated sodium bicarbonate solution and 50 ml of saturated sodiumchloride solution, dried over anhydrous magnesium sulphate andevaporated in vacuo to give 4.7 g of a pale yellow gum. Trituration ofthis gum in 10 ml of diethyl ether gave 3.8 g (82%) of tert.butyl4-(4-nitrophenyl)-2(R)-[(4-nitrophenyl)sulphonyloxy]butanoate as a paleyellow crystalline solid having a melting point of 97°-98° C.

(b) 2 g of tert.butyl9(S)-amino-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatewere added to a solution of 3.3 g of tert.butyl4-(4-nitrophenyl)-2(R)-[(4-nitrophenyl)sulphonyloxy]butanoate and 1 mlof dry triethylamine in 50 ml of dry acetonitrile and the mixture washeated under reflux for 20 hours. The resulting solution was evaporatedin vacuo, and the oily residue was dissolved in 50 ml of dichloromethaneand washed in succession with two 50 ml portions of water, 50 ml ofsaturated sodium bicarbonate solution and 50 ml of saturated sodiumchloride solution, dried over anhydrous magnesium sulphate andevaporated in vacuo to give 4 g of a yellow oil. Chromatography onsilica gel using diethyl ether for the elution gave 2.7 g (70%) oftert.butyl9(S)-[1(S))-tert.butoxycarbonyl-3-(4-nitrophenyl)propylamino]octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas a yellow oil which was identical with the compound obtained accordingto the procedure described in paragraph (A)(i).

(B) A solution of 4.63 g of tert.butyl9(S)-[1(S)-tert.butoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein 100 ml of ethanol was hydrogenated over 10% palladium-on-carbon for 3hours at room temperature and under atmospheric pressure. The catalystwas removed by filtration and the filtrate was evaporated. The resultingyellow oil was dissolved in 40 ml of ethanol, 1.72 g of1-nitroguanyl-3,5-dimethylpyrazole were added, and the solution washeated under reflux for 48 hours. The solvent was removed by evaporationand the resulting oil was chromatographed on silica gel. Elution with 3%methanol in diethyl ether followed by crystallization from ethylacetate/n-hexane gave 1.66 g of tert.butyl9(S)-[1(S)-tert.butoxycarbonyl-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas an off-white solid.

Analysis for C₂₉ H₄₅ N₇ O₇ : Calculated: C: 57.7; H: 7.5; N: 16.20%;Found: C: 57.7; H: 7.5; N: 15.95%.

(C)(i) A solution of 0.182 g of tert.butyl9(S)-[1(S)-tert.butoxycarbonyl-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein 0.6 ml of acetic acid was treated with 1.8 ml of 45% hydrogen bromidein acetic acid and the solution was stirred for 1.25 hours at 20° C. Thesolution was poured into 100 ml of anhydrous diethyl ether, stirred for2 hours and then filtered to give 0.17 g of9(S)-[1(S)-carboxy-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid hydrobromide as a white solid.

NMR: δ_(H) (CD₃ OD, 300 MHz): 1.42 (1H, m), 1.68-1.96 (4H, m), 2.09-2.35(4H, m), 2.38 (1H, m), 2.60 (1H, m), 2.78-2.96 (2H, m), 3.04 (1H, broad,d), 3.15 (1H, m), 3.48 (1H, m), 4.01 (1H, m), 4.84 (1H, t), about 4.91(1H, obscured), 7.29 (2H, d) and 7.34 (2H, d).

MS: m/e 492 (2% [M+H]⁺) and 211 (100).

(C)(ii) A solution of 6 g of tert.butyl9(S)-[1(S)-tert.butoxycarbonyl-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein 60 ml of trifluoroacetic acid was stirred at room temperature for 6hours and then concentrated in vacuo to give a gummy residue containing9(S)-[1(S)-carboxy-3-[4-(2-nitroguanidino]phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid trifluoroacetate together with excess trifluoroacetic acid. Thisgummy residue was dissolved in a mixture of 20 ml of isopropanol and 100ml of distilled water and the resulting clear solution was hydrogenatedover 10% palladium-on-carbon at room temperature and under atmosphericpressure for 24 hours. The catalyst was removed by filtration, thefiltrate was treated dropwise with ammonium hydroxide solution untilneutral (pH 7), then concentrated in vacuo to a volume of about 50 mland then left to stand at room temperature for several hours untilcrystallization was complete. The crystals were filtered off, washed insuccession with minimum volumes of distilled water, ethanol and diethylether, and finally air-dried to give 4 g of9(S)-[1(S)-carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pentalhydrate as a white crystalline solid having a melting pointof 230°-232° C. (decomposition).

EXAMPLE 2

A solution of 0.45 g of9(S)-[1(S)-ethoxycarbonyl-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid hydrobromide in a mixture of 20 ml of acetic acid, 5 ml of waterand 5 drops of hydrobromic acid was hydrog-enated over 10%palladium-on-carbon at room temperature and under atmospheric pressurefor 132 hours. The catalyst was removed by filtration and the filtratewas evaporated. The residue was stirred with 200 ml of anhydrous diethylether for 16 hours and the mixture was then filtered to give 0.57 g of9(S)-[1(S)-ethoxycarbonyl-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid dihydrobromide as an amorphous off-white solid.

NMR: δ_(H) (CD₃ OD, 300 MHz): 1.35 (3H, t), 1.44 (1H, m), 1.69-1.94 (4H,m), 2.10-2.35 (4H, m), 2.40 (1H, broad, d), 2.61 (1H, m), 2.83 (1H, m),2.92 (1H, m), 3.04 (1H, broad, d), 3.18 (1H, m), 3.49 (1H, m), 4.11 (1H,t), 4.35 (2H, m), 4.86-4.95 (2H, obscured), 7.26 (2H, d) and 7.40 (2H,d).

MS: m/e 475 (20%, [M+H]⁺) and 211 (100).

The9(S)-[1(S)-ethoxycarbonyl-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid hydrobromide used as the starting material was prepared as follows:

(A) A solution of 2.83 g of tert.butyl9(S)-amino-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylate,3.16 g of ethyl 2(R,S)-bromo-4-(4-nitrophenyl)butanoate and 1.01 g oftriethylamine in 60 ml of acetonitrile was heated to 80° C. for 15hours. The solvent was removed by evaporation and the residue waspartitioned between water and dichloromethane. The organic solution wasevaporated and the resulting oil was chromatographed on silica gel.Elution with toluene/ethyl acetate (3:2) gave 1.78 g of tert.butyl9(S)-[1(R)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas a pale yellow oil.

Analysis for C₂₆ H₃₈ N₄ O₇ : Calculated: C: 60.2; H: 7.4; N: 10.8%;Found: C: 60.1; H: 7.4; N: 10.7%.

Subsequently, using the same solvent system, there were eluted 1.93 g oftert.butyl9(S)-[1(S)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino[-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas a pale yellow oil.

Analysis for C₂₆ H₃₈ N₄ O₇ : Calculated: C: 60.2; H: 7.4; N: 10.8%;Found: C: 60.2; H: 7.3; N: 10.7%.

(B) A solution of 4.15 g of tert.butyl9(S)-[1(S)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein 200 ml of ethanol was hydrogenated over 10% palladium-on-carbon atroom temperature and under atmospheric pressure for 3 hours. Thecatalyst was removed by filtration and the volume of the filtrate wasreduced to 80 ml by evaporation. 1.76 g of1-nitroguanyl-3,5-dimethylpyrazole were added and the solution washeated under reflux for 72 hours. The solvent was removed by evaporationand the residue was partitioned between water and dichloromethane. Theorganic solution was evaporated and the residual oil was chromatographedon two columns of silica gel, with the first column being eluted withethyl acetate and the second column being eluted with diethyl ethercontaining 5% by volume of methanol. There were obtained 1.58 g oftert.butyl9(S)-[1(S)-ethoxycarbonyl-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas an orange foam.

Analysis for C₂₇ H₄₁ N₇ O₇ : Calculated: C: 56.33; H: 7.2; N: 17.0%;Found: C: 56.14; H: 7.0; N: 17.0%.

(C) A solution of 0.95 g of tert.butyl9(S)-[1(S)-ethoxycarbonyl-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein 4 ml of acetic acid was treated with 12 ml of 45% hydrogen bromide inacetic acid and stirred at 20° C. for 1 hour. The solution was pouredinto 500 ml of anhydrous diethyl ether, stirred for 1 hour and thenfiltered to give 0.89 g of9(S)-[1(S)-ethoxycarbonyl-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid hydrobromide as an amorphous white solid. NMR: δ_(H) (CD₃ OD, 300MHz): 1.33 (3H, t), 1.43 (1H, m), 1.66-1.98 (4H, m), 2.06-2.35 (4H, m),2.40 (1H, broad, d), 2.60 (1H, m), 2.73-2.96 (2H, m), 3.02 (1H, broad,d), 3.15 (1H, m), 3.47 (1H, m), 4.07 (1H, t), 4.33 (2H, m), 4.80-5.00(2H, obscured), 7.29 (2H, d) and 7.35 (2H, d).

MS: m/e 520 (2% [M+H]⁺) and 211 (100).

EXAMPLE 3

A solution of 0.39 g9(S)-[1(S)-(n-decyloxycarbonyl)-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid hydrobromide in a mixture of 16 ml of acetic acid, 4 ml of waterand 4 drops of hydrobromic acid was hydrogenated over 10%palladium-on-carbon at room temperature and at atmospheric pressure for48 hours. The catalyst was removed by filtration and the filtrate wasfreeze-dried. The resulting solid was lyophilized from water to give0.34 g of9(S)-[1(S)-(n-decyloxycarbonyl)-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid dihydrobromide as a light tan amorphous solid.

NMR: δH (CD₃ OD, 300 MHz): 0.89 (3H, m), 1.21-1.50 (17H, m), 1.66-1.99(4H, m), 2.03-2.45 (5H, m), 2.61 (1H, m), 2.74-2.98 (2H, m), 3.04 (1H,broad, d), 3.18 (1H, m), 3.49 (1H, m), 4.13 (1H, t), 4.20-4.40 (2H, m),4.82-5.00 (2H, obscured), 7.26 (2H, d) and 7.40 (2H, d).

MS: m/e 587 [13% (M+H)⁺ ]and 211 (100).

The9(S)-[1(S)-(n-decyloxycarbonyl)-3-[4-(2-nitroguanidinophenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid hydrobromide used as the starting material was prepared as follows:

(A) A solution of 2.07 g of tert.butyl9(S)-[1(S)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylate, prepared asdescribed in Example 2(A), in 10 ml of ethanol was treated with 10 ml of1M aqueous sodium hydroxide solution. The resulting solution was stirredat 20° C. for 5 hours and then diluted with water. The ethanol wasremoved by evaporation. The aqueous solution was adjusted to pH 4 andthen extracted with dichloromethane. The organic solution was evaporatedto give a yellow foam. 0.49 g of the foam was added to a solution of0.81 g of 1,1'-carbonyldiimidazole and 1.42 g of methyl iodide in 5 mlof dichloromethane which had been stirred at 20° C. for 3 hours. 0.158 gof n-decanol was added and the solution was stirred at 20° C. for afurther 24 hours. The mixture was partitioned between dichloromethaneand dilute hydrochloric acid. The organic solution was evaporated andthe resulting oil was chromatographed on silica gel. Elution withdiethyl ether/n-hexane (2:1) gave 0.19 g of tert.butyl9(S)-[1(S)-(n-decyloxycarbonyl)-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo-[1,2-a][1,2]diazepine-1(S)-carboxylateas a yellow oil.

NMR: δ_(H) (CDCl₃, 300 MHz): 1.88 (3H, m), 1.17-1.41 (17H, m), 1.48 (9H,s), 1.57-1.82 (4H, m), 1.87-2.12 (4H, m), 2.30 (1H, m), 2.50 (1H, m),2.82-3.13 (4H, m), 3.35 (1H, t), 3.42 (1H, m), 4.05-4.22 (3H, m), 4.94(1H, m), 7.37 (2H, d) and 8.14 (2H, d).

MS: m/e 630 (3%, M⁺), 501 (37), 211 (56), 179 (83), 143 (87) and 57(100).

(B) A solution of 2.017 g of tert.butyl9(S)-[1(S)-(n-decyloxycarbonyl)-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein 25 ml of ethanol was hydrogenated over 10% palladium-on-carbon atroom temperature and under atmospheric pressure for 18 hours. Thecatalyst was removed by filtration and the filtrate was evaporated togive 1.9 g of tert.butyl9(S)-[3-(4-aminophenyl)-1(S)-(n-decyloxycarbonyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas a colorless oil.

Analysis for C₃₄ H₅₆ N₄ O₅ : Calculated: C: 68.0; H: 9.4; N: 9.3%;Found: C: 68.1; H: 9.7; N: 9.2%.

(C) A solution of 1.67 g of tert.butyl9(S)-[3-(4-aminophenyl)-1(S)-(n-decyloxycarbonyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateand 0.611 g of 1-nitroguanyl-3,5-dimethylpyrazole in 25 ml of ethanolwas heated under reflux for 72 hours. The solvent was removed byevaporation and the residue was chromatographed on silica gel using 3%methanol in diethyl ether for the elution. Material of Rf 0.4 (5%methanol in diethyl ether) was partitioned between diethylether/n-hexane and water. The organic phase was separated and evaporatedto give 0.76 g of tert.butyl9(S)-[1(S)-[n-decyloxycarbonyl)-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas an off-white foam.

Analysis for C₃₅ H₅₇ N₇ O₇ : Calculated: C: 61.1; H: 8.35; N: 14.25%;Found: C: 61.0; H: 8.45; N: 14.10%.

(D) A solution of 0.70 g of tert.butyl9(S)-[1(S)-(n-decyloxycarbonyl)-3-[4-(2-nitoguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein 2.5 ml of acetic acid was treated with 8.0 ml of 45% hydrogen bromidein acetic acid and the solution was stirred at 20° C. for 1 hour. Thesolution was poured into 200 ml of anhydrous diethyl ether, stirred for2 hours and then filtered to given 0.54 g of9(S)-[1(S)-(n-decyloxycarbonyl)--[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid hydrobromide as an off-white amorphous solid.

Analysis for C₃₁ H₄₉ N₇ O₇.HBr: Calculated: C: 52.20; H: 7.07; N: 13.75;Br; 11.21% Found: C: 51.85; H: 6.95; N: 13.51; Br; 11.23%.

EXAMPLE 4

A solution of 0.34 g of9(S)-[1(S)-[[2-(1-adamantyl)ethoxy]carbonyl]-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]-1(S)-carboxylicacid hydrobromide in 16 ml of acetic acid and 4 ml of water containing afew drops of hydrobromic acid was hydrogenated over 10%palladium-on-carbon at room temperature and under atmospheric pressurefor 48 hours. The catalyst was removed by filtration and the filtratewas lyophilized to give 0.4 g of9(S)-[1(S)-[[2-(1-adamantyl)ethoxy]carbonyl]-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid dihydrobromide as a white amorphous solid.

NMR: δ_(H) (CD₃ OD, 300 MHz): 1.51 (3H, m), 1.60 (6H, s), 1.64-2.03(13H, m), 2.06-2.36 (4H, m), 2.43 (1H, m), 2.60 (1H, m), 2.74-2.97 (2H,m), 3.04 (1H, m), 3.15 (1H, m), 3.52 (1H, m), 4.02 (1H, t), 4.36 (2H,m), 4.77-5.07 (2H, obscured), 7.25 (2H, d) and 7.38 (2H, d).

MS: m/e 609 (20% [M+H]⁺) and 211 (100).

The9(S)-[1(S)-[[2-adamantyl)ethoxy]carbonyl]-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a[1,2]diazepine-1(S)-carboxylicacid hydrobromide used as the starting material was prepared as follows:

(A) A solution of 2.95 g of tert.butyl9(S)-[1(S)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2-]diazepine-1(S)-carboxylatein 32 ml of ethanol was treated with 28.5 ml of 0.5M aqueous sodiumhydroxide solution at 20° C. for 16 hours. The mixture was diluted withwater and the ethanol was removed by evaporation. The aqueous solutionwas adjusted to pH 6 and extracted with dichloromethane. The organicsolution was then evaporated to give 2.62 g of a yellow solid. 2.3 g ofthis solid were added to a solution of 3.80 g of 1,1'-carbonyldiimidazoland 6.66 g of methyl iodide in 25 ml of dry dichloromethane which hadbeen stirred at 20° C. for 3 hours. After 1 hour, 0.84 g of 1-adamantaneethanol was added and the solution was then stirred at 20° C. for 16hours. The mixture was then filtered, the filtrate was diluted withdichloromethane, washed in sequence with 2M aqueous hydrochloric acid,water, 5% aqueous sodium bicarbonate solution and water, and thenevaporated. Chromatography on two columns of silica gel, usingchloroform/methanol/acetate/acid/water (120:15:3:2) for the elution ofthe first column and diethyl ether for the elution of the second column,gave 1.84 g of tert.butyl9(S)-[1(S)-[[2-(1-adamantylethoxy]carbonyl]-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas a pale yellow oil.

(B) A solution of 1.84 g of tert.butyl9(S)-[1(S)-[[2-(1-adamantyl)ethoxy]carbonyl]-3-(4-nitrophenyl)propylamino]-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein 25 ml of ethanol was hydrogenated over 10% palladium-on-carbon atroom temperature and under atmospheric pressure for 16 hours. Thecatalyst was removed by filtration and the filtrate was evaporated togive 1.8 g of a pale yellow oil. A solution of 1.6 g of this oil and0.56 g of 1-nitroguanyl-3,5-dimethylpyrazole in 20 ml of ethanol washeated under reflux for 72 hours while stirring. The mixture was thenevaporated and the residue was chromatographed on two columns of silicagel, using diethyl ether containing 3% by volume of methanol for theelution of the first colum and ethyl acetate for the elution of thesecond column. There was obtained 0.50 g of tert.butyl9(S)-[1(S)-[[2-(1-adamantyl)ethoxy]carbonyl]-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein the form of a white foam.

Analysis for C₃₇ H₅₅ N₇ O₇ : Calculated: C: 62.60; H: 7.81; N: 13.81%;Found: C: 62.52; H: 7.82; N: 13.86%.

(C) A solution of 0.45 g of tert.butyl9(S)-[1(S)-[[2-(1-adamantyl)ethoxy]carbonyl]-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein 1.5 ml of acetic acid was treated with 5 ml of 45% hydrogen bromidein acetic acid and the mixture was stirred at 20° C. for 1 hour. Thesolution was poured into 200 ml of anhydrous diethyl ether, stirred for1 hour and then filtered to give 0.53 g of9(S)-[1(S)-[[2-(1-adamantyl)ethoxy]carbonyl]-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid hydrobromide as a white solid.

NMR: δ_(H) (CD₃ OD, 300 MHz): 1.50 (3H, m), 1.58 (6H, s), 1.63-2.00(13H, m), 2.07-2.36 (4H, m), 2.41 (1H, m), 2.61 (1H, m), 2.74-2.98 (2H,m), 3.05 (1H, broad, d), 3.17 (1H, m), 3.48 (1H, m), 4.06 (1H, t), 4.33(2H, m), 4.82-4.97 (2H, obscured) and 7.32 (4H, m).

MS: m/e 654 (3% [M+H]⁺) and 211 (100).

EXAMPLE 5

A solution of 0.48 g of9(S)-[N-benzyl-1(S)-ethoxycarbonyl)-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pivaloyloxy methyl ester in 20 ml of acetic acid and 5 ml of waterwas hydrogenated over 10% palladium-on-carbon at room temperature andunder atmospheric pressure for 30 hours. The catalyst was removed byfiltration and the filtrate was lyophilized. The resulting gum waschromatographed on silica gel using chloroform/methanol/aceticacid/water (120:15:3:2) for the elution to give 0.19 g of9(S)-[1(S)-ethoxycarbonyl-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pivaloyloxy methyl ester acetate as an off-white amorphous solid.

Analysis for C₂₉ H₄₄ N₆ O₇.1:1C₂ H₄ O₂ : Calculated: C: 57.39; H: 7.46;N: 12.95%; Found: C: 56.90; H: 7.52; N: 12.87%.

NMR: δ_(H) (CDCl₃, 300 MHz): 1.21 (9H, s), 1.28 (3H, t), 1.34-2.12 (9H,m), 1.97 (3H, s), 2.28 (1H, m), 2.32 (1H, m), 7.74 (2H, m), 2.95 (1H,m), 3.08 (1H, m), 3.31 (1H, t), 3.35 (1H, m), 4.14 (1H, m), 4.20 (2H,m), 5.02 (1H, m), 5.74 (1H, d), 5.83 (1H, d), 7.14 (2H, d) and 7.24 (2H,d).

MS: m/e 589 (30%, [M+H]⁺), 211 (80) and 149 (100).

The9(S)-[N-benzyl-1(S)-ethoxycarbonyl-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pivaloyloxy methyl ester used as the starting material was preparedas follows:

(A) 5.09 g of tert.butyl9(S)-amino-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylate,1.91 g of benzaldehyde and 3 g of 3A molecular sieve in 54 ml of ethanolwere stirred for 3 hours and then hydrogenated over 5%palladium-on-carbon at room temperature and under atmospheric pressurefor 1.75 hours. The catalyst was removed by filtration and the filtratewas evaporated. Chromatography of the residue on silica gel usingdiethyl ether/methanol (39:1) for the elution gave 5.25 g of tert.butyl9(S)-benzylamino-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas a pale yellow oil.

NMR: δ_(H) (CDCl₃, 300 MHz): 1.37 (1H, m), 1.47 (10H, m), 1.65-1.84 (3H,m), 1.92 (1H, m), 2.07 (1H, m), 2.31 (1H, broad, d), 2.52 (1H, m), 2.94(1H, broad, d), 3.07 (1H, m), 3.28 (1H, broad, s), 3.41 (1H, m), 3.68(1H, d), 3.89 (1H, d), 4.23 (1H, t), 4.97 (1H, m) and 7.20-7.44 (5H, m).

(B) A solution of 1.87 g of tert.butyl9(S)-benzylamino-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylate,1.93 g of ethyl2(R)-trifluoromethanesulphonyloxy-4-(4-nitrophenyl)butanoate and 0.7 gof triethylamine in 5 ml of acetonitrile was stirred at 20° C. for 2hours. A further 0.2 g of ethyl2(R)-trifluoromethanesulphonyloxy-4-(4-nitrophenyl)butanoate and 0.05 gof triethylamine were added and the solution was then left to stand at20° C. for 16 hours. The solvents were removed by evaporation and theresidue was partitioned between water and dichloromethane. Evaporationof the organic solution followed by chromatography on silica gel usingdiethyl ether/n-hexane (1:1) for the elution gave 2.44 g of tert.butyl9(S)-[N-benzyl-1(S)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylateas a pale yellow oil.

Analysis for C₃₃ H₄₄ N₄ O₇ : Calculated: C: 65.11; H: 7.29; N: 9.20%;Found: C: 65.41; H: 7.15; N: 9.20%.

(C) A solution of 2.0 g of tert.butyl9(S)-[N-benzyl-1(S)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylatein 10 ml of trifluoroacetic acid was stirred at 20° C. for 2.5 hours andthen left to stand at 0° C. for 16 hours. 20 ml of toluene were addedand the solution was evaporated. The residue was dissolved indichloromethane, washed with water and sodium chloride solution, andthen evaporated. Chromatography on silica gel usingdichloromethane/methanol (19:1) for the elution gave 0.9 g of9(S)-[N-benzyl-1(S)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid as a pale yellow oil.

NMR: δ_(H) (CDCl₃, 300 MHz): 1.33 (4H, m), 1.62 (1H, m), 1.71-2.09 (7H,m), 2.40 (1H, m), 2.45-2.59 (2H, m), 2.66 (1H, m), 3.00 (1H, broad, d),3.17 (1H, m), 3.29 (2H, m), 4.01-4.20 (2H, m), 4.23 (1H, d), 4.39 (1H,d), 4.75 (1H, t), 4.84 (1H, m), 7.13 (2H, d), 7.19-7.40 (5H, m) and 8.04(2H, d).

MS: m/e 553 (2%, [M+H]⁺) and 211 (100).

(D) A solution of 2.68 g of9(S)-[N-benzyl-1(S)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid in 10 ml of acetone was treated with 0.32 g of potassium hydroxidein 0.5 ml of water, 0.73 g of chloromethyl pivalate and 0.12 g of sodiumiodide. The mixture was heated under reflux for 5 hours and thenpartitioned between water and dichloromethane. The organic phase wasevaporated and the residue was chromatographed on silica gel usingdiethyl ether/n-hexane (1:1) for the elution, to give 1.72 g of9(S)-[N-benzyl-1(S)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pivaloyloxy methyl ester as a pale yellow oil.

Analysis for C₃₅ H₄₆ N₄ O₉ : Calculated: C: 63.05; H: 6.95; N: 8.40%;Found: C: 62.81; H: 6.84; N: 8.22%.

(E) A mixture of 1.66 g of9(S)-[N-benzyl-1(S)-ethoxycarbonyl-3-(4-nitrophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pivaloyloxy methyl ester and 0.97 g of powdered zinc in 35 ml of85% acetic acid was stirred at 20° C. for 3 hours. Excess zinc wasremoved by filtration and the filtrated was evaporated. The residue waspartitioned between water and dichloromethane and the organic phase wasevaporated. The resulting oil was taken up in 25 ml of ethanol and thesolution was treated with 0.55 g of 1-nitroguanyl-3,5-dimethylpyrazole.The solution was then heated under reflux for 72 hours while stirring. Afurther 0.55 g of 1-nitroguanyl-3,5-dimethylpyrazole was added and themixture was heated under reflux for a further 24 hours while stirring.The mixture was then evaporated to dryness and the residue waschromatographed on silica gel using diethyl ether/methanol (39:1) forthe elution to give 0.58 g of9(S)-[N-benzyl-1(S)-ethoxycarbonyl-3-[4-(2-nitroguanidino)phenyl]propylamino]-octahydro-1oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pivaloyloxymethyl ester as an off-white foam.

Analysis for C₃₆ H₄₉ N₇ O₉ : Calculated: C: 59.74; H: 6.82; N: 13.55%;Found: C: 59.75; H: 6.85; N: 13.38%.

The following additional Examples illustrate pharmaceutical preparationscontaining9(S)-[1(S)-carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid dihydrobromide (Compound A) as the active ingredient.

EXAMPLE A

Tablets containing the following ingredients can be produced in aconventional manner:

    ______________________________________                                        Ingredient       Per tablet                                                   ______________________________________                                        Compound A        10.0 mg                                                     Lactose          125.0 mg                                                     Maize starch      75.0 mg                                                     Talc              4.0 mg                                                      Magnesium stearate                                                                              1.0 mg                                                      Tablet weight    215.0 mg                                                     ______________________________________                                    

EXAMPLE B

Capsules containing the following ingredients can be produced in aconventional manner:

    ______________________________________                                        Ingredient       Per capsule                                                  ______________________________________                                        Compound A        25.0 mg                                                     Lactose          150.0 mg                                                     Maize starch      20.0 mg                                                     Talc              5.0 mg                                                      Capsule fill weight                                                                            200.0 mg                                                     ______________________________________                                    

We claim:
 1. A pyridazodiazepine compound of the formula ##STR11##wherein R¹ and R² each independently are hydrogen, C₁ -C₁₀ -alkyl,adamantyl-(C₁ -C₄ -alkyl) or (C₂ -C₆ -alkanoyloxy)-(C₁ -C₄ -alkyl), aswell as pharmaceutically acceptable salts thereof.
 2. A compoundaccording to claim 1, wherein R¹ is hydrogen, C₁ -C₁₀ -alkyl oradamantyl-(C₁ -C₄ -alkyl).
 3. A compound according to claim 2, whereinR¹ is hydrogen, ethyl, n-decyl or 1-adamantylethyl.
 4. A compoundaccording to claim 1, wherein R² is hydrogen or (C₂ -C₆-alkanoyloxy)-(C₁ -C₁₄ -alkyl).
 5. A compound according to claim 4,wherein R² is hydrogen or pivaloyloxymethyl.
 6. A compound according toclaim 1, wherein the H₂ N--C(NH)--NH--group is situated in thepara-position of the phenyl ring.
 7. A compound according to claim 1,wherein R¹ is hydrogen, ethyl, n-decyl or 1-adamantylethyl, R² ishydrogen or pivaloyloxymethyl, and the H₂ N--C(NH)--NH--group issituated in the para-position of the phenyl ring.
 8. A compoundaccording to claim 1 which is9(S)-[1(S)-carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid, or a pharmaceutically acceptable salt thereof.
 9. A compoundaccording to claim 1 which is9(S)-[1(S)-carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid dihydrobromide.
 10. A compound according to claim 1 which is9(S)-[1(S)-ethoxycarbonyl-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid, or a pharmaceutically acceptable salt thereof.
 11. A compoundaccording to claim 1 which is9(S)-[1(S)-(n-decyloxycarbonyl)-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid, or a pharmaceutically acceptable salt thereof.
 12. A compoundaccording to claim 1 which is9(S)-[1(S)-[[2-(1-adamantyl)ethoxy]carbonyl]-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid, or a pharmaceutically acceptable salt thereof.
 13. A compoundaccording to claim 1 which is9(S)-[1(S)-ethoxycarbonyl-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pivaloyloxymethyl ester, or a pharmaceutically acceptable saltthereof.
 14. A pharmaceutical composition for treating or preventinghigh blood pressure containing an amount effective to treat or preventhigh blood pressure of a compound having the formula ##STR12## whereinR¹ and R² each independently are hydrogen, C₁ -C₁₀ -alkyl, adamantyl-(C₁-C₄ -alkyl) or (C₂ -C₆ -alkanoyloxy)-(C₁ -C₄ -alkyl), or apharmaceutically acceptable salt thereof, and one or moretherapeutically inert excipients.
 15. A composition according to claim14, wherein R¹ is hydrogen, C₁ -C₁₀ -alkyl or adamantyl-(C₁ -C₄ -alkyl).16. A composition according to claim 15, wherein R¹ is hydrogen, ethyl,n-decyl or 1-adamantylethyl.
 17. A composition according to claim 14,wherein R² is hydrogen or (C₂ -C₆ -alkanoyloxy)-(C₁ -C₄ -alkyl).
 18. Acomposition according to claim 17, wherein R² is hydrogen orpivaloyloxymethyl.
 19. A composition according to claim 14, wherein theH₂ N--C(NH)--NH-- group is situated in the para-position of the phenylring.
 20. A composition according to claim 14, wherein R¹ is hydrogen,ethyl, n-decyl or 1-adamantylethyl, R² is hydrogen or pivaloyloxymethyl,and the H₂ N--C(NH)--NH-- group is situated in the para-position of thephenyl ring.
 21. A composition according to claim 14 in which the activecompound is9(S)-[1(S)-Carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid or a pharmaceutically acceptable salt thereof.
 22. A compositionaccording to claim 14 in which the active compound is9(S)-[1(S)-carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid dihydrobromide.
 23. A composition according to claim 14 in whichthe active compound is9(S)-[1(S)-ethoxycarbonyl-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]-diazepine-1(S)-carboxylicacid or a pharmaceutically acceptable salt thereof.
 24. A compositionaccording to claim 14 in which the active compound is9(S)-[1(S)-(n-decyloxycarbonyl)-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]-diazepine-1(S)-carboxylicacid or a pharmaceutically acceptable salt thereof.
 25. A compositionaccording to claim 14 in which the active compound is9(S)-[[2-(1-adamantyl)ethoxy]carbonyl]-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid or or a pharmaceutically acceptable salt thereof.
 26. A compositionaccording to claim 14 in which the active compound is9(S)-[1(S)-ethoxycarbonyl-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pivaloyloxymethyl ester or a pharmaceutically acceptable saltthereof.
 27. A method of treating or preventing high blood pressurewhich comprises administering to a patient requiring such treatment aneffective amount of a pyridazodiazepine derivative of the formula##STR13## wherein R¹ and R² each independently are hydrogen, C₁ -C₁₀-alkyl, adamantyl-(C₁ -C₄ -alkyl) or (C₂ -C₆ -alkanoyloxy)-(C₁ -C₄-alkyl), or a pharmaceutically acceptable salt thereof.
 28. A methodaccording to claim 27, wherein R¹ is hydrogen, C₁ -C₁₀ -alkyl oradamantyl-(C₁ -C₄ -alkyl).
 29. A method according to claim 29, whereinR¹ is hydrogen, ethyl, n-decyl or 1-adamantylethyl.
 30. A methodaccording to claim 27, wherein R² is hydrogen or (C₂ -C₆-alkanoyloxy)-(C₁ -C₄ -alkyl).
 31. A method according to claim 30,wherein R² is hydrogen or pivaloyloxymethyl.
 32. A method according toclaim 27, wherein the H₂ N--C(NH)--NH-- group is situated in thepara-position of the phenyl ring.
 33. A method according to claim 27,wherein R¹ is hydrogen, ethyl, n-decyl or 1-adamantylethyl, R² ishydrogen or pivaloyloxymethyl, and the H₂ N--C(NH)--NH-- group issituated in the para-position of the phenyl ring.
 34. A method accordingto claim 27 in which the compound is9(S)-[1(S)-carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid or a pharmaceutically acceptable salt thereof.
 35. A methodaccording to claim 27 in which the compound is9(S)-[1(S)-carboxy-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid dihydrobromide.
 36. A method according to claim 27 in which thecompound is9(S)-[1(S)-ethoxycarbonyl-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]-diazepine-1(S)-carboxylicacid or a pharmaceutically acceptable salt thereof.
 37. A methodaccording to claim 27 in which the compound is9(S)-[1(S)-(n-decyloxycarbonyl)-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]-diazepine-1(S)-carboxylicacid or a pharmaceutically acceptable salt thereof.
 38. A methodaccording to claim 27 in which the compound is9(S)-[1(S)-[[2-(1-adamantyl)ethoxy]carbonyl]-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid or a pharmaceutically acceptable salt thereof.
 39. A methodaccording to claim 27 in which the compound is9(S)-[1(S)-ethoxycarbonyl-3-(4-guanidinophenyl)propylamino]-octahydro-10-oxo-6H-pyridazo[1,2-a][1,2]diazepine-1(S)-carboxylicacid pivaloyloxymethyl ester or a pharmaceutically acceptable saltthereof.